Refrigerator control



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R. W. HASTINGS REFRIGERATOR CONTROL Filed July 1, 1937 March 5, 1940.

WITN ESSES:

Patented Mar. 5, 194% STATES REFRIGERATOR CONTROL Roger W. Hastings, Springfield, Mass, assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa, a

Pennsylvania corporation of Application July 1, 1937, Serial No. 151,326

Claims.

My invention relates to control means for refrigerating apparatus and has for an object to provide improved means of this character.

A further object of my invention is to main- 5 tain the temperature of the air in a refrigerated chamber below a predetermined maximum value regardless of the temperature of the ambient atmosphere.

It is a further object of this invention to normally control the operation of a refrigerating machine in accordance with the temperature of the air in the zone being cooled and to operate the machine independently of the air temperature when the temperature of the cooling element rises to a predetermined value.

It is a further object of my invention to control a refrigerating machine by a pair of thermal responsive elements responding, respectively, to the temperatures of the cooling element and the air cooled thereby, one of said elements operating between wider temperature limits than the other of the elements.

These and other objects are eflfected by my invention as will be apparent from the follow- 5 ing description and claims taken in connection with the accompanying drawing, forming a part of this application, in which:

The single figure of the drawing diagrammatically shows a refrigerating machine controlled in accordance with my invention.

Referring now to the drawing, I show my improved control applied-to refrigerating apparatus of the household type and including a cabinet it formed of insulated wall members It and defining a chamber or zone M for the storage of articles to be refrigerated. The air in the zone it is cooled by an evaporator It of any suitable type and which may be provided with shelf members it for the support of trays N5 in which fluid to be congealed may be disposed.

Refrigerant vaporized in the evaporator I3 is withdrawn through a conduit it by a compressor tl, driven by a motor it. The withdrawn vapor is compressed by the compressor W to a 5 relatively high pressure and is discharged through a conduit t9 into a condenser 21, the latter being cooled in any suitable manner, such as, for example, by a fan 22. The refrigerant in the condenser 2! is condensed at relatively 50 high pressure and the liquid refrigerant is conveyed to the evaporator by means of a conduit 23 having a suitable expansion device 2k connected therein, the latter functioning to reduce the pressure of the condensed refrigerant to the 55 value maintained in the evaporator. I3. .Vaporization of the condensed refrigerant is effected in the evaporator I13 at relatively low pressure. The apparatus described in the foregoing paragraphs operates on the well known compressorcondenser-expander cycle as will be apparent to those skilled in the art. t

It has, heretofore, been the practice to control a refrigerating machine in response to the temperature of the cooling element or in response to the temperature of the air in the zone 10 cooled thereby. In the first case, the temperature of the air may fluctuate substantially due to variations in temperature of the ambient atmosphere, variations of the heat load or to frequent opening of the door or what may be it termed servicing load. This condition is present because an interval of time prevails between the change in condition and the reflection of the change by the evaporator thermostat. The thermostat does, however, respond quickly to changes in evaporator temperature so that quick freezing may be readily accomplished.

In the second case or where the temperature of the air is the controlling factor, quick response to changing heat and servicing loads and to varg iations in the ambient temperature is obtained but the system does not respond readily to quick freezing demand .causing rises in the evaporator temperature' In accordance with my invention, I provide a 39 pair of thermostats for controlling the refrigerating unit, one of which responds to air temperature and the second of which is responsive to evaporator temperature. The first thermostat exerts what I term normal control over the 35 system and the system, therefore, quickly reflects changes in heat and servicing loads and variations in the temparature of the ambient atmosphere. The temperature of the evaporator at this time is maintained preferably below freezing so that products stored therein are maintained frozen. When the evaporator is subjected to a high heat load due, for example, to the insertion of a pan of warm water, the second thermostat quickly reflects the change in temperature and effects operation of the system. The first thermostat operates between relatively close temperature limits and the second or evaporator thermostat between relatively wide temperature limits and is effective to start and stop the system only when the evaporator is subjected to a heavy heat load.

In the drawing, the thermostats responsive to the air temperature and the evaporator temperature are shown generallyat 25 and 26, respec tively. The thermostat 25 includes a thermal responsive element 21 disposed in heat transfer relation with the air in the chamber I2 and connected to an expansible bellows 28, the latter actuating an electric switch 29. An adjustable spring 38 biases the bellows 28 in opposition to the pressure therein and determines the temperatures at which the switch 29 is opened and closed. The thermostat 25 is of the well known expansible gas type and no further description of it is deemed necessary.

The thermostat .25 may be similar in construction to the thermostat 25 and has a thermal responsive element 32 disposed in intimate heat transfer relation with the evaporator l3. The thermostat 26 includes a bellows 33, a switch 3E actuated thereby and an adjusting device 35. I have shown the thermostats 25 and 26 of the expansible gas type but it will be understood that they may be of any known type suitable for this service.

The motor I8 is energized from a suitable source of power shown as line conductors L1 and L2 under control of the switches 29 and 34, the latter being connected in parallel motor circuits 3B and 37, respectively. A switch 38 may be provided for rendering the system active and inactive.

As described heretofore, the thermostat 25'is adjusted to operate between relatively close temperature limits and the thermostat 26 between relatively wide limits so that, during normal operation, the motor I8 is started and stopped by the thermostat 25. For example, the thermostat 25 may be adjusted to close and open its switch 29 when the temperature of the air in the zone I! attains values of 48 F. and 45 F., respectively. At this time, the evaporator operates between 30 F. and 24 F. The thermostat 26 may be adjusted to close its switch 36 at 32 F. and to open the same at a lower value such as, for example, 20 F.

Operation As shown in the drawing, the switches 29 and 34 are open so that the motor I8 and compressor 11 are inactive. A rise in temperature of the air in the space i2 to 48 F. effects closure of the switch 29 and operation of the compressor l1. At this time, the evaporator temperature is approximately 30 F. Evaporation of refrigerant depresses the evaporator temperature to 24 F. and the air temperature to 45 F. at which time the thermostat switch 29 opens for terminating operation of the compressor.

A rise in the ambien t or room temperature increases the heat flow to theair in the space l2 through the walls II. This increased heat flow tends to increase the temperature of the air in the space but any rise is quickly reflected by the thermostat 25 and the air temperature will be maintained between the given values of 48 F. and 45 F. An increased heat load such as caused by frequent servicing will be quickly reflected by the thermostat 25 in the same manner so that the air temperature is maintained at the given values.

Assume that the evaporator temperature is increased to 32 F. or above due to the insertion of a tray of warm water therein; This increased load is reflected by the thermostat 26 quickly or before the thermostat 25 would be affected. Closure of the switch 34 causes operation of the compressor l1 and evaporation of refrigerant for the freezing of the water. The temperature of the evaporator is gradually reduced and, when greases the temperature has b een depressed to 20 F., the switch 3G is opened. At this time, the air temperature is reduced to approximately 44 F. The subsequent starting and stopping of the compressor I! will be eflected by the thermostat 25 in the absence of any further load which would affect the evaporator temperature prior to the air temperature.

From the foregoing, it will be apparent that I have provided an improved control mechanism for a refrigerating system wherein the temperature of the air in the refrigerated zone is maintained between desirable limits regardless of variations in ambient temperatures or heat load and wherein the evaporator responds quickly for freezing operation.

I have shown my invention applied to a refrigerating machine of the compressor-condenser-expander type, but it will be understood that it is not so limited and may be applied to other types.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by the prior art or as are specifically set forth in the appended claims.

What I claim is:

1. In refrigerating apparatus, the combination of means defining a space to be cooled, an evaporator for cooling the air in said space, means for circulating refrigerant through said evaporator, means responsive to predetermined high and low temperatures of the air in said space for initiating and terminating operation of the circulating means whereby the evaporator normally operates between high and low temperature values, and means operative simultaneously with the first mentioned temperature responsive means and responsive to a predetermined temperature of the evaporator higher in value than said normal high operating temperature of the evaporator, for initiating operation of the circulating means and responsive to a predetermined temperature of the evaporator lower in value than said normal low operating temperature of the evaporator, for terminating operation of the circulating means.

2, In refrigerating apparatus, the combination of means defining a space to be cooled, an evaporator for cooling the air in said space, means for circulating refrigerant through said evaporator, means responsive to a condition of the air in said space for controlling the operation of said refrigerant circulating means whereby the evaporator is normally operated between high and low temperatures and means effective at all times for operation simultaneously with said controlling means and responsive to a predetermined high temperature of the evaporator, higher in value than said normal maximum operating temperature of the evaporator for initiating operation of the circulating means and responsive to a predetermined low temperature of the evaporator, lower in value than said normal minimum operating temperature of the evaporator for terminating operation of the refrigerant circulating means.

3. In refrigerating apparatus, the combination of means defining a space to be refrigerated, evaporating means for cooling said space, means for translating refrigerant to the evaporating means for evaporation, means responsive to a contemperature value and higher in value than said low temperature value.

4. In refrigerating apparatus, the combination of means defining a zone to be refrigerated, an evaporator for cooling the air in said zone and having means for receiving substances to be cooled to a relatively low temperature, means for circulating refrigerant through said evaporator, means responsive to the temperature of the air for controlling the circulating means whereby the evaporator is operated normally between high and low temperature values, and means effective at all times for operation simultaneously with said controlling means and responsive to a predetermined temperature of the evaporator higher in value than said normal high temperature of the evaporator for initiating operation of the circulating means and responsive to a predetermined temperature of the evaporator lower in I value than said normal low temperature of the evaporator for terminating operation of the circulating means.

5. The combination as claimed in claim 4 wherein at least one of the temperature responsive means includes means for manually adjusting at will, the temperatures to which it responds.

ROGER W. HASTINGS. 

